@article{0004-637X-538-2-766,
  author={M. C. McCarthy and A. J. Apponi and C. A. Gottlieb and P. Thaddeus},
  title={Laboratory Detection of Five New Linear Silicon Carbides: SiC3, SiC5, SiC6, SiC7, and SiC8},
  journal={The Astrophysical Journal},
  volume={538},
  number={2},
  pages={766},
  url={http://stacks.iop.org/0004-637X/538/i=2/a=766},
  year={2000},
  abstract={The rotational spectra of five highly polar linear silicon-carbon chains SiC n , n = 3 and 5-8, were detected by Fourier transform microwave spectroscopy in a supersonic molecular beam among the products of a gas discharge through silane and diacetylene; SiC 3 was detected as well by conventional millimeter-wave absorption spectroscopy in a large glow discharge through silane and acetylene. The electronic ground state was found to be X 1 Σ + for those with even n and X 3 Σ - for those with odd n , in agreement with recent ab initio calculations. The rotational and centrifugal distortion constants of all five molecules were determined to high accuracy, as were the spin-spin and spin-rotation coupling constants for triplet SiC 3 , SiC 5 , and SiC 7 . A fairly steep increase in the magnitude of the spin-spin constant with chain length, similar to that found previously for the C n and C n O chains, was observed for the present silicon carbides. Of the five new silicon carbides, SiC 3 is of particular astronomical interest because radio emission lines of the isomeric ground state, a compact rhomboidal ring, have recently been detected in IRC+10216 and because this chain is calculated to possess a large dipole moment of 4.8 D and to lie only 5 kcal mol -1 above ground. From the laboratory data, the most intense transitions of SiC 3 can now be calculated to better than 1 km s -1 in equivalent radial velocity at frequencies up to 300 GHz.}
}